South African actress Charlize Theron poses during a photocall to promote "The Burning Plain" in Madrid March 5, 2009. [Agencies]

Charlize Theron says the current marriage laws are a "form of apartheid".

The South African-born actress - who has previously stated she will not marry her long-term partner Stuart Townsend until same-sex marriage is legal in the US - can't understand why America refuses to give gay people the same rights as their heterosexual counterparts.

"It's not the reason I'm not getting married but it's maybe a part of it. My ability to get married is a piece of me that I wish I could give to somebody who it would mean so much to. We should all have the chance. It's just so caveman, I can't believe we're still talking about it."

Charlize, 33, praised 'Milk' - which won Sean Penn a Best Actor Oscar for his portrayal of gay politician Harvey Milk - for helping keep the issue in the public consciousness.

She said: "I just loved the film, I absolutely loved the film. I loved the way it was embraced and the speeches and this conversation that we're constantly having about this issue, I don't want that to go away, I want us to keep having it."